Liquid crystal display device and manufacturing method therefor

ABSTRACT

The present invention includes a liquid crystal display device having an oxide film having high adhesiveness to a substrate to thereby prevent oxidation of a wiring material or the like, and includes, an electrode or a terminal electrode having high conductivity, and a manufacturing method therefor. Consequently, in the present invention, a liquid crystal display device has an electrode terminal of a TFT substrate, wherein the electrode is formed on an insulator and is comprised of a conductive layer mainly consisting of copper and an oxide covering an outer part, further the oxide is a layered structure of transparent electrodes, the layered portion having ohmic contact, and the oxide mainly consists of manganese oxide.

This application claims priority under 35 U.S.C. §120 as a continuationof U.S. patent application Ser. No. 11/784,879, filed Apr. 10, 2007,entitled “LIQUID CRYSTAL DISPLAY DEVICE AND MANUFACTURING METHODTHEREFOR.”

TECHNICAL FIELD

The present invention relates to a liquid crystal display deviceprovided with wiring mainly consisting of copper (Cu) covered with anoxide film containing Mn (Mn-containing oxide film) and to amanufacturing method therefor. More particularly to an externalextraction electrode terminal structure used in the liquid crystaldisplay device, specially to a liquid crystal display device providedwith the external extraction electrode terminal structure covered withan oxide and to a manufacturing method therefore.

BACKGROUND OF INVENTION

In recent years, a low-power-consumption liquid crystal display device(LCD) that is thin, lightweight, and capable of being driven by lowervoltage has been widely used. In such a liquid crystal display device, ascreen size has been increasing year after year and a display of movingimages just like TV images has been required. To meet such requirements,wiring should be configured with a low-resistive and high conductivematerial.

Along with such increase in the screen size of the liquid crystaldisplay device, a gate wiring material has been changed from molybdenumalloy to aluminum alloy or aluminum clad. However, aluminum (Al) hasproblems of hillock and electromigration.

For example, as disclosed in Patent Document 1, Japanese publishedunexamined patent application No. 2000-199054, a wiring materialconsisting of Al—Nd alloy has been proposed, and anodized Al,Mo-alloy-cladded Al, or double-layered Al has been used. The Al—Nd alloyhas a resistivity of 5.1 μΩ·cm while pure Al has a resistivity of 2.5μΩ·cm.

Therefore, in order to use pure Al in practice, wiring having athree-layered structure of Ti/Al/Ti or Mo/Al/Mo is used as measures forthe hillock and the electro-migration. However, this causes an increasein film formation steps, which remains as a problem.

On the other hand, copper has drawn attention as a material havingresistivity lower than those of the above-described gate electrodematerials. However, copper has problems of not only poor adhesiveness toglass used as a TFT substrate in an LCD, but also of being easilyoxidized when an insulation layer is formed.

For this reason, a technique using alloyed copper wiring has recentlybeen attempted in a TFT-LCD in order to solve such problems. Thistechnique is intended to make an alloying element form reaction productswith a substrate to thereby ensure adhesiveness to the substrate as wellas to make an additive element form oxide on the Cu surface to therebymake the oxide act as an oxidation resistant film for Cu.

However, with this proposed technique, intended characteristics have notbeen adequately developed. That is, electrical resistance of Cu becomeshigher because the alloying element remains in Cu, and thereforeadvantages over wiring materials using Al or Al alloy have not been ableto be exhibited.

Further, as described in Patent Document 2, Japanese publishedunexamined patent application No. 2004-163901, in order to use thecopper wiring for a TFT-LCD, a technique to ensure adhesiveness andbarrier characteristics to a substrate by the formation of a Mo alloyfilm between Cu and the substrate has been considered.

However, this technique has problems of an increase in process steps,i.e., a step of forming the Mo alloy film, as well as of an increase inwiring effective resistance. Further, a Cu single layer is used forsource and drain electrodes, however, there remains a problem in itsstability.

Also in Patent Document 3, Japanese published unexamined patentapplication No. 2004-139057, a technique in which a refractory nitridesuch as TaN, TiN, or WN is formed around Cu is proposed to solve suchproblems regarding the Cu wiring. However, compared with theconventional wiring materials, this technique has disadvantages ofrequiring another material to form a barrier layer and additionalprocess steps, and of increasing effective resistance of wiring becausea high-resistive barrier layer is thickly formed.

Further, Patent Document 4, Japanese published unexamined patentapplication No. 2005-166757 discloses a method for improvingadhesiveness and oxidation resistance by the addition of one or moreelements selected from Mg, Ti, or Cr to TFT-LCD wiring. However, thistechnique has a problem that the additive element remains in the wiring,causing an increase in wiring resistance. Also, the additive elementreduces oxide in a substrate and the reduced element is diffused in thewiring, causing a problem of an increase in the wiring resistance.

Patent Document 5, Japanese published unexamined patent application No.2002-69550 discloses a method for improving oxidation resistance by theaddition of 0.3 to 10 wt. % of Ag to Cu. However, this technique hasproblems that adhesiveness to a glass substrate is not improved andoxidation resistance sufficient to resist liquid crystal processingcannot be obtained.

Patent Document 6, Japanese published unexamined patent application No.2005-158887 proposes copper alloy prepared by the addition of 0.5 to 5wt. % of at least one element of Ti, Mo, Ni, Al, or Ag to Cu to improveadhesiveness. However, there is a problem of an increase in electricalresistance of wiring due to the additive element.

Patent Document 7, Japanese published unexamined patent application No.2004-91907, proposes a method for suppressing oxidation by the additionof 0.1 to 3.0 wt. % of Mo to Cu followed by the segregation of the addedMo at grain boundaries. However, although this technique is capable ofimproving oxidation resistance of Cu, it has a problem of an increase inwiring resistance.

In Patent Document 8, W02006-025347, copper alloy prepared by theaddition of an appropriate additive element to Cu is used, wherein theadditive element forms an oxide film to become a passivation film, whichsuppresses oxidation of Cu, and the passivation film is also formed atan interface with an adjacent insulation layer, which suppressesinterdiffusion. Consequently, copper wiring having high conductivity andsuperior adhesiveness to a substrate is provided. Further, a liquidcrystal display device using such copper wiring is provided. Inaddition, it is suggested that one of such additive elements preferablybe Mn.

In Patent Document 9, Japanese granted patent publication No. 3302894, aTFT structure used in TFT-LCD is proposed and a TFT structure, wherein agate electrode coated with an oxide film when a Cu alloy is applied tothe gate electrode, is specifically presented. In the document, it ispresented that when Cu is a first metal, the second metal is at leastone type chosen from Ti, Zr, Hf, Ta, Nb, Si, B, La, Nd, Sm, Eu, Gd, Dy,Y, Yb, Ce, Mg, Th, and Cr. However, the additive element of this secondmetal is different from that of the current invention. An externalextraction electrode structure is not mentioned in any of thesedocuments. However, high adhesiveness to a substrate, resistance to ause environment, and stability as an electrical contact of externalextraction electrode are required to the external extraction electrodestructure, and they are important components for a liquid crystaldisplay device.

As described above, in these conventional techniques, an attempt toensure adhesiveness to a substrate and oxidation resistance by theaddition of an alloying additive element to Cu has been made, however,none of them has achieved a satisfactory result. Also, a satisfactoryresult has not been achieved regarding high adhesiveness to a substrate,resistance to a use environment, or stability as an electrical contactof external extraction electrode which are required to the externalextraction electrode structure.

Especially, although Patent Document 8, WO2006-025347, suggests a liquidcrystal display device using such copper wiring, the suggested techniquealone is not able to provide a satisfactory configuration to realize agate wiring structure to be used for the liquid crystal display device.Also, in the Patent Document 9, the oxide film for coating the gateelectrode is specified as the oxide film mainly comprising the secondmetal formed by thermally treating in an oxygen ambient, however, it isnot only unexplained but also not even indicated in the Patent Document9 that the thermal treatment induces the reaction between Cu alloy andSi oxide film in contact with the Cu alloy, thereby forming an oxidefilm covering the gate electrode, which ensures adhesiveness with asubstrate. In addition, the external extraction electrode structure isnot mentioned.

That is, all the difficulties in forming a Cu alloy film with lessprocess steps, lowering effective resistance of wiring, and improvingadhesiveness to a glass substrate must be solved, however, with theabove conventional techniques, these difficulties cannot be solved, andproduct manufacturing is practically difficult.

The present invention has been made in consideration of such situations,and it is therefore the object of the present invention to form an oxidefilm having high adhesiveness to a substrate to thereby preventoxidation of a wiring material or the like, and also to provide a liquidcrystal display device provided with wiring, an electrode or a terminalelectrode having high conductivity, and a manufacturing method therefor.Further, another object of the present invention is to form the wiring,electrode, or terminal electrode applicable to practical manufacturingprocessing while simultaneously accomplishing all the above objects.

BRIEF SUMMARY OF INVENTION

In order to accomplish the above objects, in an electrode terminal of aTFT substrate consisting of a liquid crystal display device, theelectrode terminal formed on an insulator is comprised of a conductivelayer mainly consisting of copper and an oxide covering the conductivelayer mainly consisting of copper, further the oxide having a layeredstructure of transparent electrodes, and the layered portion is in ohmiccontact.

The oxide may be an oxide layer containing Mn mainly and Cusubsidiarily.

Further, the oxide has compositional formula of Cu_(X)Mn_(Y)Si_(Z)O(0<X<Y, 0<Z<Y).

Also, the electrode terminal formed on an insulating layer is covered bya protective layer and the transparent electrode may be contacted to theoxide through an opening portion of the protective layer.

The oxide layer mainly comprised of copper is formed from a copperalloy, and an additive element in the copper alloy may be Mn.

An additive amount of Mn may be in a range of 0.5 to 25 atomic %.

The oxide layer may contain Cu and Si.

In order to accomplish the above objects as another invention, in anexternal extraction electrode terminal of a TFT substrate consisting ofa liquid crystal display device, the electrode terminal formed on ainsulator has a structure of being held between two different insulationlayers or insulators, and the structure is comprised of a first layermainly consisting of copper and a second layer consisting of an oxidecovering an outer circumferential part of the first layer, further thesecond layer has a compositional formula of Cu_(X)MnYSi_(Z)O (0<X<Y,0<Z<Y).

This first layer is formed from a copper alloy, and an additive elementof the copper alloy may be at least one type of metal selected from agroup consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd.

Also the first layer is formed from a copper alloy, and an additiveelement in the copper alloy may be Mn.

Further, an additive amount of Mn may be in a range of 0.5 to 25 atomic%.

Also, the second layer may be an oxide layer containing Mn mainly and Cusubsidiarily.

The insulation layer or the insulation film holding the wiring orelectrode in-between may be a glass plate.

The second layer may contain Cu and Si.

In order to accomplish the above objects as another invention, in anelectrode terminal on a TFT substrate consisting of a liquid crystaldisplay device, by thermally treating the copper alloy layer mainlycomprising copper formed on a glass at approximately 150° C. toapproximately 300° C., an additive element of said copper alloy mayreact with silicon oxide in the glass and form an oxide covering anouter circumferential part of said copper alloy layer.

Further, contact resistance may be configured to decrease after peakingat approximately 250° C. of the thermal treatment temperature for thecopper alloy layer.

Film thickness of the oxide layer covering an outer circumferential partof the copper alloy layer may be 1 to 30 nm.

Further, in order to accomplish the above objects as another invention,in an external extraction electrode terminal of a TFT substrateconsisting a liquid crystal display device, the electrode terminalformed on an insulator has a structure of being held between twodifferent insulation layers or insulators, and the structure iscomprised of a first layer mainly consisting of copper and a secondlayer consisting of an oxide covering an outer circumferential part ofthe first layer, further the second layer has a compositional formula ofCu_(X)MnYSi_(Z)O (0<X<Y, 0<Z<Y).

This first layer is formed from a copper alloy, and an additive elementof the copper alloy may be at least one type of metal selected from agroup consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd.

This first layer is formed from a copper alloy, and an additive elementin the copper alloy may be Mn.

An additive amount of Mn may be in a range of 0.5 to 25 atomic %.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram of a cross-section of a liquid crystaldisplay (LCD) module.

FIG. 2 is a conceptual diagram of a cross-section of an LCD panel.

FIG. 3 is a conceptual diagram of an IPS liquid crystal.

FIG. 4 is a plan view of a pixel part and a TFT part.

FIG. 5 is a cross-sectional view of a pixel part and a TFT part.

FIG. 6 is an equivalent circuit diagram of a pixel part and a TFT part.

FIG. 7 is a cross-sectional view of a TFT (staggered top gatestructure).

FIG. 8 is a cross-sectional view of a TFT (inversely staggered channelstopper structure).

FIG. 9 is a cross-sectional view of a TFT (inversely staggered channeletch structure).

FIG. 10 is a cross-sectional view of a terminal portion of a liquiddisplay device (LCD) module.

FIG. 11 is a cross-sectional view of a terminal portion of a liquiddisplay device (LCD) module.

FIG. 12 is a cross-sectional view of a terminal portion of a liquiddisplay device (LCD) module.

FIG. 13 is a cross-sectional view of a terminal portion of a liquiddisplay device (LCD) module.

FIG. 14 is a cross-sectional view of a terminal portion of a liquiddisplay device (LCD) module.

FIG. 15 is a measurement result of I-V characteristics.

FIG. 16 is a measurement result of I-V characteristics.

FIG. 17 is a measurement result of I-V characteristics.

FIG. 18 is a measurement result of I-V characteristics.

FIG. 19 is a measurement result of I-V characteristics.

FIG. 20 is one example (1) of a cross-section of a pixel part and a TFTpart of the present invention.

FIG. 21 is a graph illustrating electrical resistivity (1) of copperalloy (CuMn).

FIG. 22 is a graph illustrating electrical resistivity (2) of copperalloy (CuMn).

FIG. 23 is an operating waveform diagram of a TFT.

FIG. 24 is a diagram illustrating a model of a propagation delay of agate voltage pulse.

FIG. 25 is an example of adhesion strength measured by a nanoscratchtest, compared with a case of forming Ta that is frequently used insemiconductor wiring.

FIG. 26 is a composition diagram of a wiring structure.

FIG. 27 is an enlarged view of a composition of a wiring structureacross the interface between Cu and SiO2.

FIG. 28 is a cross-section TEM picture after thermally treating Cu—Mnalloy on the glass at 250° C. for 10 minutes.

FIG. 29 is a result of an adhesiveness evaluation by tape test afterthermally treating Cn—Mn alloy formed on a glass substrate at eachtemperature for a predetermined time.

FIG. 30 shows resistivity of the alloy thin film that was thermallytreated at 350° C., and a time change in thickness of a Mn oxide formedon the Cu surface.

FIG. 31 is a diagram illustrating the fundamentals of a TFTmanufacturing process.

FIG. 32 is a diagram illustrating a five-mask process in TFTmanufacturing.

FIG. 33 is a cross-sectional view of a TFT manufactured by the five-maskprocess.

FIG. 34 is a cross-sectional view of an electrode led outside.

FIG. 35 is a plan view of a pixel part.

FIG. 36 is a cross-sectional photograph of an oxide film layer forwiring.

FIG. 37 is a diagram illustrating a composition of an oxide film layerfor wiring.

FIG. 38 is a film thickness of an oxide layer.

FIG. 39 is diagram of a cross-sectional model of a wiring structureaccording to the present invention.

FIG. 40 is one example of a cross-section of an organic EL element.

FIG. 41 is one example of an equivalent circuit diagram of a pixel in anorganic EL display.

FIG. 42 is one example of a cross-section of an organic EL display.

DETAILED DESCRIPTION OF INVENTION

Embodiments of the present invention will hereinafter be described withreference to drawings. In the embodiments, a technique in which copperalloy of the present invention is applied to wiring constituting eachelectrode and a matrix of an a-Si TFT on a TFT substrate is described.First, a liquid crystal display device used for the present invention isdescribed below.

FIG. 1 is a conceptual diagram illustrating a cross-section of a liquidcrystal display (LCD) module. The display size of a liquid crystaldisplay device has been increasing, and consequently an active matrixLCD is utilized. One representative of such LCDs is a TFT-LCD in whichan LCD is driven by thin film transistors (TFTs). FIG. 1 represents sucha TFT-LCD module. The TFT-LCD module is comprised of an LCD panel 1, adriving circuit 2, a backlight 3, and a chassis 4. The LCD panel 1consists of a TFT substrate 11 and a color filter (CF) substrate 12,which are arranged on lower and upper sides respectively.

The driving circuit 2 serves to externally apply electrical signals tothe LCD panel 1 to drive it. The driving circuit 2 is comprised of anLCD driver LSI chip 21 or an LCD driver LSI multilayered printed circuitboard (PCB) 22, and a control circuit 23. The LCD driver LSI chip 21 orLCD driver LSI is electrically connected to terminal electrodes of theLCD panel through an anisotropic conductive film. To such aconfiguration, a backlight unit 38 and a light guide plate 39 areattached, and chassis 4 completes the module structure.

FIG. 2 is a conceptual diagram illustrating a cross-section of the LCDpanel 1. A liquid crystal layer (LC layer) 13 is formed in a spacebetween the TFT substrate 11 and the CF substrate 12. A size of thespace is approximately 3 to 5 μm and controlled by the arrangement ofspacers 14 inside the panel. The liquid crystal layer is in a liquidstate and sealed with surrounding sealing 15. In the liquid crystallayer, the arrangement of liquid crystal molecules is controlled so thatthey function as an optical crystal. The liquid crystal molecules arearranged vertically or horizontally with respect to interfaces that areinner faces of the substrates. This arrangement is called anorientation.

Oriented films 17 are coated onto the inner faces of the TFT substrate11 and the CF substrate 12, i.e., on the liquid crystal layer sides.Further, polarizer films 18 and 19 are placed on the outer faces of theTFT substrate 11 and the CF substrate 12. On the TFT substrate 11, a TFT111, a holding or a storage capacitor (Cs) 112, and a pixel electrode113 are arranged. The combination of the TFT 111, the storage capacitor112, and the pixel electrode 113 is a basic configuration of one pixel.Several million pixels are arranged in one LCD panel. Therefore, suchpixels are connected in a matrix form through wiring on the TFTsubstrate 11.

The opposite CF substrate 12 is comprised of a black matrix (BM) 121, acolor filter (CF) 122 consisting of three primary colors (red, green,and blue), and a common electrode 123. The common electrode 123 istypically placed on the CF substrate side, however, in an IPS liquidcrystal (In-Plane Switching Nematic Liquid Crystal) mode, it is placedon the TFT substrate 11. A schematic diagram of the IPS liquid crystalis shown in FIG. 3.

In FIG. 2, the common electrode 123 is a transparent electrode, and usesindium tin oxide (ITO), indium zinc oxide (IZO) or indium tin zinc oxide(ITZO). In order to lead it outside, it is led to the TFT substrate 11through a short part 161. Each electrode is electrically connected tothe driving circuit 2 through a connection pad 162. Also, the TFTsubstrate 11 and the CF substrate 12 require transparency to light, anduse a hard glass. See U.S. Pat. Nos. 2,701,698 and 5,598,285 for moreinformation on the IPS liquid crystal as shown in FIG. 3.

FIG. 4 is a plan view, a cross-sectional view, and an equivalent circuitdiagram of a pixel part 31 and a TFT part 32. Each pixel is connected toa gate wiring 33 and a signal wiring 34. Accordingly, as shown in theplan view of FIG. 4, the TFT part has three kinds of electrodes, i.e., agate electrode 351, a source electrode 352, and a drain electrode 353.The drain electrode 353 is connected to the pixel electrode 113 via athrough-hole

As can be seen from a cross-sectional view in FIG. 5, amorphous silicon(a-Si) 36 is used as semiconductor, and silicon nitride SiN_(X), asilicon oxide film SiO_(X), a multilayered film of them, or an organicmaterial layer is used as a gate insulation film 37. Expressing eachpixel part as the equivalent circuit diagram (FIG. 6) results in theaddition of parasitic capacitances C_(gs), C_(gd), and C_(ds) betweenrespective electrodes of the TFT. A liquid crystal layer is arrangedbetween a pixel electrode 113 and a common electrode 123 on an oppositesubstrate, and expressed as C_(1c) in the equivalent circuit diagram.Parallel to C_(lc), a storage capacitor C_(s) is formed.

FIGS. 7, 8, and 9 show three kinds of a-Si TFT structures, i.e., astaggered top gate structure, an inversely staggered channel stopperstructure, and an inversely staggered channel etch structure. Amongthem, the channel etch structure shown in FIG. 9 is often used inpractice.

Next, detail for applying this copper alloy to the electrode terminalfor extracting outward, which connects the TFT-LCD panel and the driverLSI as a drive circuit, in the liquid crystal display device accordingto the present intervention is now explained. In the TFT-LCD of theliquid crystal display device according to the present invention, thegate wiring using copper wiring typified by CuMn, and the electrodeterminal 33 of the signal wiring comprise a structure that covers awiring with the oxide product 47 by going through a production processas described later.

This oxide product 47 mainly consists of manganese oxide, and mayinclude copper (Cu) or silicon (Si). This enables stability to theatmosphere, and additionally, as for connectivity to the drive circuit,sufficient conductivity of the contact portion can be secured by thermalcompression bonding or voltage application because this oxide layer 47has a thickness of a few nanometers (nm). Further, the oxide product isformed between the substrate which is an insulator, such as a glass, andhas a high adhesiveness with the substrate.

Such embodiments are shown in FIG. 10 to FIG. 19. Normally, a layerstructure with ITO, IZO, or ITZO which is a transparent electrode 71,such as FIGS. 10 and 11, is employed to ensure environmental resistance.The thickness of this oxide layer 47 is a few nm in this structurethereby adequate conductivity can be secured by voltage application. Inaddition, by configuring as shown in FIG. 20 in the present invention,the current process can be used for the manufacturing method, therebythe present invention can be realized without significantly changing themanufacturing process.

Further, this oxide product 47 prevents Cu from penetrating into thetransparent electrode 71, thereby providing a terminal structure havinga superior environmental resistance. Still further, as shown in FIGS. 11and 13, the environmental resistance can be secured when the filmthickness of this oxide layer is nm to tens of nm, and the electrodeterminal can be formed by a single layer of copper electrode. In thiscase, an electrical connection with an anisotropically-conductive filmcan be made by a thermal compression bond. Moreover, FIG. 14 shows astructure of an electrode that has a protective layer 44 removed.

[Ohmic Contact]

In the external extraction electrode structure, stability of electricalcontact is required. Each contact portion is preferably to be in ohmiccontact electrically. In the present invention, the external extractionelectrode terminal mainly comprised of copper is covered by an oxidelayer mainly comprised of manganese oxide. Although such thin oxidelayer mediates, stable ohmic contact can be obtained. Such anexperimental example is described below. The result of contactresistance is measured by the Transfer Length Method (TLM). Cu-4atomic %Mn is formed on a transparent electrode (ITO) substrate in a thicknessof 200 nm. Onto the substrate, placing a molybdenum mask with theopening diameter of 0.5 mm and the distance of an opening edge of 0.5 mm(distance between the center of the opening is 1 mm), then Cu—Mn isformed. Thereby, round electrodes of Cu—Mn are formed at equalintervals.

FIGS. 15 to 18 shows measurement results of I-V characteristics bycontacting a prober to two different electrodes. The spacing betweenelectrodes was changed to obtain the I-V characteristics. The contactresistance value was able to be obtained from these measurement results.In FIG. 15 to FIG. 18, I-V characteristics are showing linearity at eachexperimental parameter, thus demonstrating that ITO and Cu—Mn are inohmic contact. Results for the thermal treatment with varioustemperatures showing similar results and ohmic contacts are formed. Atthis time, FIG. 15 shows I-V characteristics when the thermal treatmenttemperature is 150° C. and the treatment time is 30 minutes. FIG. 16shows I-V characteristics when the thermal treatment temperature is 200°C. and the treatment time is 30 minutes. FIG. 17 shows I-Vcharacteristics when the thermal treatment temperature is 250° C. andthe treatment time is 30 minutes. FIG. 18 shows I-V characteristics whenthe thermal treatment temperature is 300° C. and the treatment time is30 minutes.

Regarding the results for heat treatment with these varioustemperatures, FIG. 19 plots the contact resistance in the vertical axisand the thermal treatment temperature in the transverse axis. As theheat treatment temperature rises, the value of contact resistance alsoincreases because the thickness of the barrier layer increases. Thisresult verifies that the layered portion of the electrode mainlycomprised of copper, which has an oxide layer mainly comprised ofmanganese oxide mediated, and the transparent electrode is an ohmiccontact. For this reason, this experimental result shows stability as anelectrical contact, instead of the ohmic contact from the tunnel effectthat we initially anticipated. In FIG. 19, when the thermal treatmenttemperature exceeds 250° C., the contact resistance value virtuallysaturates. For this reasons, a terminal with an appropriate contactresistance value can be formed during normal manufacturing processes ofliquid crystal display devices without providing a special thermaltreatment process.

Also, the oxide layer mainly comprised of Mn oxide has a thickness of afew nm, thus an application of voltage may cause a dielectric breakdownand leads to a good conductivity. However, slight instability remains inthis conductivity that causes dielectric breakdown. From theexperimental results of the present invention, which demonstrates thatthe contact with ITO which is mediated by the oxide layer, and Cu—Mn isohmic, instead of the contact that causes such dielectric breakdown. Forthis reason, the contact of the present invention shows electricalstability.

[Cu Alloy]

An additive element in the copper alloy applied to the liquid crystaldisplay device of the present invention will be described below. Theadditive element in the copper alloy applied to the gate wiring 33 andthe gate electrode 351 in the TFT-LCD regarding the liquid crystaldisplay device of the present invention is a metal that has an oxideformation free energy with a negative value larger than that of Cu and adiffusion coefficient of the additive element in Cu (hereinafterreferred to as a “diffusion coefficient” unless otherwise noted) largerthan a self-diffusion coefficient of Cu.

By selecting the additive element of which the diffusion coefficient islarger than the self-diffusion coefficient of Cu, the additive elementcan reach the Cu surface faster to preferentially form an oxide filmlayer comprising the additive element on the Cu alloy surface.

In other words, if the diffusion coefficient of the additive element issmaller than the self-diffusion coefficient of Cu, the additive elementrequires a significant amount of time to reach the Cu alloy surface, andtherefore a Cu oxide film layer consisting of CuO, Cu₂O, and the like isformed on the Cu alloy surface.

In this case, because the Cu oxide film layer is not robust, oxygenintrudes into the inside of the Cu oxide film layer and forms oxide ofthe additive element in the Cu alloy. In addition, an amount of Cu in ametal state decreases as the oxidation of Cu progresses, and if such Cualloy is used for wiring of a liquid crystal display device, itselectrical resistance would be increased.

Accordingly, the copper alloy applied to the present invention wasintended to provide a solution to such a problem by the selection of theadditive element of which the diffusion coefficient is larger than theself-diffusion coefficient of Cu.

The additive element in the copper alloy, which is applied to thepresent invention, is now described in detail. It is preferable that theadditive element in the copper alloy forms a solid solution in anadditive amount ranging from 0.1 to 25 atomic % in the Cu alloy. This isbecause the additive element cannot be easily diffused if it is notwithin the solid solution range in the Cu alloy. Especially, if theadditive element forms an intermetallic compound with Cu, it is hardlydiffused.

Also, if the amount of the additive element in the Cu alloy is lowerthan 0.1 atomic %, the oxidation of Cu cannot be prevented because theoxide film layer to be formed becomes thin. On the other hand, if theamount of the additive element exceeds 25 atomic %, the additive elementis sometimes precipitated as a secondary phase.

Specifically, the additive element in the Cu alloy applied to thepresent invention is at least one of the elements selected from thegroup consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd.A single element may be used, or a plurality of additive elements may beapplied together. Manganese (Mn) is especially preferable. Into the Cualloy, an impurity such as S, Se, Te, Pb, or Si may be mixed in,however, this is acceptable as long as the characteristics of the Cualloy, including electrical conductivity and tensile strength, are notdeteriorated. The additive elements do not always have to be evenlydistributed in the Cu alloy. In other words, the additive elements canbe distributed unevenly in the Cu alloy. For example, the additiveelements can be distributed only in the upper or lower part of the Cualloy. When the additive elements are distributed only in one part ofthe Cu alloy, the other part of the Cu alloy is pure Cu.

In the present invention, a method for forming the Cu alloy is notparticularly limited. That is, a plating method such as electric fieldplating or molten plating, or a physical vapor deposition method such asvacuum evaporation or sputtering may be used. The Cu alloy deposited byany of the methods is thermally treated to form an oxide film layer.

Temperature for the thermal treatment is, for example, 150 to 450° C.,and a time period for the thermal treatment is, for example, in a rangeof 2 minutes to 5 hours. If the thermal treatment temperature is lowerthan 150° C., productivity is reduced because the formation of the oxidefilm is time-consuming. On the other hand, if it exceeds 450° C., itcauses a problem that Cu is oxidized to form an oxide film before anadditive element in the Cu alloy is diffused and reaches a surface.Also, if the thermal treatment time period is shorter than 2 minutes,thickness of the oxide film is too thin, while if it exceeds 5 hours,the formation of the oxide film is too time-consuming.

One example providing low resistivity in one of the copper alloys usedin the present invention, Cu—Mn, is now described. By the thermaltreatment, Cu—Mn constitutes wiring or an electrode, and an oxide filmlayer covering it. An example of a relationship between the thermaltreatment time period (second) and resistivity (μΩ·cm) of the wiringbody is shown in FIG. 21, using oxygen concentration (ppm) in a thermalatmosphere as a parameter.

Measurements in FIG. 21 were carried out in such a way that Cu and Mncontaining oxide was first formed also in a surface layer portion on thetop side of the wiring body, then the oxide layer in the top surfacelayer portion was removed to expose the Cu wiring body, and theelectrical resistivity of the Cu wiring body was measured. According tothe result, the resistivity of the Cu wiring body was extremely low, and2.2 μΩ·cm under the conditions of an oxygen concentration of 50 ppm anda thermal treatment time period of 4 minutes. This value was close to anelectrical resistivity of 1.7 μΩ·cm of a pure Cu bulk material. That is,a satisfactory value to provide low resistive wiring and to promote animage quality improvement in a TFT-LCD was realized.

Because most of the Mn escapes from the thin film of Cu—Mn by thethermal treatment and forms an oxide layer, thus the wiring body canrealize the resistivity close to that of a pure copper.

Similarly, FIG. 22 shows an example of relative resistivity againstthermal treatment temperature using a thermal treatment time period as aparameter. It turns out that the resistivity is saturated to lowresistivity at a thermal treatment temperature of 150 to 400° C. and athermal treatment time period of approximately 2 minutes. The timeperiod is short enough for processing time, and is an adequate value formanufacturing a TFT-LCD.

[Shading]

Among improvements of image quality obtained by lowering the wiringresistance, which are remarkable effects of the present invention, ashading reduction effect will be described below. First, an operation ofa TFT-LCD is described in detail. A display device used in the presentinvention is an LCD in which pixels are arranged in a matrix form. ThisLCD is called an active matrix LCD (AM-LCD).

For example, in the case of a TFT-LCD for a digital TV, the number ofpixels in a full HD specification is (1920×3)×1080. That is, the numberof scanning lines is 1080, and the number of signal lines is 5760because one pixel consists of three primary colors (red, green, andblue) and therefore the number of pixels in a horizontal direction istripled. In this TFT-LCD, gate voltage V_(G) shown in FIG. 23 is appliedto a gate electrode of the TFT constituting the pixel. Typically, V_(G)is 10 to 15 V.

On the other hand, signal voltage V_(S) is applied to a sourceelectrode, and a gate voltage pulse serves as a scanning signal. Giventhat a frame frequency to display one screen is 60 Hz, a frame time is16.7 ms. If the 1080 scanning lines are scanned in a line sequentialscanning mode, a gate voltage pulse width becomes approximately 16 μs.

As illustrated in FIG. 23, a cycle of the gate voltage pulse is 16.7 ms,and the pulse width is approximately 16 μs. On the other hand, giventhat a LCD drive voltage V_(lc) is approximately 5 V, the signal voltageapplied to the source electrode to drive a liquid crystal isapproximately 10 V that is a double of the voltage amplitude. Adifference between the signal voltage and a common voltage V_(com)applied to the common electrode provides a liquid crystal layer drivevoltage V_(p) (t), and FIG. 23 exemplifies a driving waveform in a frameinversion system in which a polarity of V_(p) (t) is inverted for eachframe to transform it into an alternating voltage.

In this case, transmittance of the LCD modulates the brightness of thedisplay by voltage modulation of the signal voltage. Further, the liquidcrystal drive voltage is retained while the gate voltage pulse is off(approximately 16 ms that substantially corresponds to the frame time).

FIG. 23 illustrates such a situation. The liquid crystal layer drivevoltage consists of a writing state and a holding state. Also, thetransmittance of the LCD depends on a root-mean-square (rms) value ofthe liquid crystal layer drive voltage V_(p) (t). For this reason, theLCD drive voltage V_(lc) is expressed by the following equation 1:

$\begin{matrix}{{\left\langle {Vlc} \right\rangle{rms}} = {\frac{1}{2{Tf}}\sqrt{{\int_{t = 0}^{2{Tf}}\left\lbrack {{{Vp}(t)} - {Vcom}} \right\rbrack^{2}}\ }{\mathbb{d}t}}} & (1)\end{matrix}$Meanwhile, a switching time of the a-Si TFT is of the order of μsbecause capacitance loads are driven and mobility of a-Si is as low as0.3 to 1.0. Accordingly, a few μs is required for switching-on of theTFT during the gate voltage pulse width of 16.7 μs.

Further, because the liquid crystal layer is a capacitance load, anapplication of the signal voltage is delayed. As a result, rise of theliquid crystal layer drive voltage V_(p) (t) is also delayed. Inaddition, in a TFT-LCD for TV with a full HD specification, 5760 pixelsare arranged in one line. Plurality of TFTs, arranged in one line, aresimultaneously excited by applying the gate voltage pulse to an end partof the gate wiring.

At this time, the gate voltage pulse is propagated from the end part togate electrodes of respective pixels. A propagation speed decreases as aresistance value and parasitic electrical capacitance of the gate wiringare increased. This phenomenon is referred to as a propagation delay ofthe gate voltage pulse. As the propagation delay becomes larger,adequate time to input the liquid crystal layer drive voltage cannot beobtained, and therefore the liquid crystal drive voltage for each pixelcannot reach a predetermined value. As a result, the transmittance ofthe liquid crystal layer becomes uneven, i.e., the screen brightnessbecomes uneven, causing the shading. It should be appreciated that alsoin the above-described IPS liquid crystal and VA liquid crystal, it maycause the shading in the same manner.

A model of the propagation delay of the gate voltage pulse describedabove is shown in FIG. 24. Each pixel on the gate wiring can beequivalently expressed using resistance R and parasitic capacitance C.An RC delay of the gate voltage pulse in each column is accumulated, andat a terminal node n5760, the propagation delay reaches several μs.

If a distribution of the LCD brightness at this time is schematicallyillustrated, the brightness is gradually varied along the gate wiring ina normally white mode LCD, and at the terminal, the screen is brightinstead of black as originally intended due to insufficient liquidcrystal layer drive voltage. Therefore, the propagation delay of thegate voltage pulse is reduced by lowering the gate wiring resistance.Consequently, the unevenness in the screen brightness, in other words,the shading can be suppressed.

The present invention enables a reduction in such shading by using theabove-described copper wiring close to pure copper, as illustrated inFIG. 14.

On the other hand, the number of nodes in the source wiring is 1080, andthe problem of propagation delay is low compared to the gate wiring.However, as the size of a LCD panel increases, the value of propagationdelay in the source wiring reaches a considerable length, such as 1-3μs, thus decreasing this propagation delay by applying Cu—Mn alloy tothe source wiring is effective for decreasing the unevenness in the LCDdisplay brightness.

[Adhesiveness to Glass]

Adhesiveness to glass that is another remarkable effect of the presentinvention herein described. Thin film wiring and electrodes formed fromthe copper alloy Cu—Mn are covered with the oxide layer formed by thethermal treatment.

In a liquid crystal display device, such wiring and electrodes areessentially required to have excellent adhesiveness to a glass substrateand the insulation layer. The adhesiveness is typically determined byperforming a tape test. As shown in Table 1, if a pure Cu thin film isformed on an insulation film SiO₂, sufficient adhesiveness cannot beobtained, causing separation.

TABLE 1 Tape test results of Cu and Cu/Mn double layered film on aninsulation film SiO₂ Material Thermal treatment temperature (° C.)(thickness: nm) 150° C. 200° C. 250° C. 300° C. 350° C. 400° C. 450° C.Cu (150 nm) X X X X X X X Cu(150)/Mn(2)stacked layer Δ ◯ ◯ ◯ ◯ ◯ ◯Cu(150)/Mn(20)stacked layer Δ ◯ ◯ ◯ ◯ ◯ ◯ ◯: Good adhesiveness X:Separation (poor adhesiveness) Δ: Partial Separation

On the other hand, in a case of a double-layered thin film of Cu and Mn,interdiffusion of Mn and Si occurs at an interface between them by athermal treatment, and an oxide layer having a composition ofCu_(X)Mn_(Y)Si_(Z)O (0<X<Y, 0<Z<Y) is formed at the interface. Thisenables excellent adhesiveness to the insulation layer SiO₂ to beobtained.

As the tape test to evaluate the adhesiveness, a separation state wasevaluated when a tape was peeled off after the tape had been stuck on aCu thin film surface. Before the tape is peeled off, it is bonded ontothe surface by pressing with a nail.

This procedure is repeated 10 times on a same position of the thin filmto check the adhesiveness to a substrate. Results of the tape test wereanalyzed in detail.

According to the results, the Cu/Mn double-layered thin film exhibitedlow electrical resistivity by being thermally treated at 200° C. orhigher. On the other hand, regarding the adhesiveness, partialseparation was observed when the film was thermally treated at 150° C.By a thermal treatment at 250° C., excellent adhesiveness was exhibitedin all the thermal treatment time periods, which are 3 minutes, 30minutes, 1 hour, 20 hours, and 100 hours. Similarly, excellentadhesiveness was obtained when the thermal treatment temperature was350° C.

FIG. 25 shows an interface adhesion strength in the case of thermallytreated Cu-4atomic % Mn alloy at 400° C. for 30 minutes after forming ina film on a SiO₂ substrate, compared with a case of forming Ta(frequently used for semiconductor wiring), between pure Cu and SiO₂.The adhesion strength is measured by a nano scratch method. A horizontalaxis indicates a scratch time required to scan a length of 6 μm on thefilm surface. A smaller time corresponds to a faster scratch speed. Atany scratch speed, the load value required for interface separation islarger in Cu—Mn/SiO₂ compared to Cu/Ta/SiO₂, showing a higher adhesionstrength.

The oxide layer constituting the interface with the wiring and theelectrodes on the insulation film SiO₂ has the composition ofCu_(X)Mn_(Y)Si_(Z)O as shown in FIGS. 26 and 27, and is amorphous. Asdescribed, at the interface, the oxide layer containing mainly Mn actsas an excellent diffusion barrier to prevent interdiffusion between Cuwiring and the insulation layer. The gradual concentration change nearthe interface of the oxide layer promotes an excellent adhesion of theoxide layer with the Cu and with the SiO₂. It can be considered thatthis provides the excellent adhesiveness.

This enables the oxide film with high adhesiveness to a substrate to beformed to prevent oxidation of a wiring material or the like, and aliquid crystal display device having wiring, an electrode, or a terminalelectrode with high electrical conductivity and a manufacturing methodtherefore to be provided. All of such difficulties are simultaneouslyovercome, and the wiring, electrode, or terminal electrode applicable toa practical manufacturing process can be formed.

In addition, Cu-4atomic % Mn alloy is formed in a film on the glasssubstrate using a sputter deposition system in the current invention.Thereafter, the film is thermally treated in a pure argon atmospherewithin a temperature range of 150-350° C. The time required for thethermal treatment was 10 to 60 minutes. An evaluation (a tape test) isperformed to find out whether the thin film strips off or not by peelinga piece of scotch tape adhered to the alloy thin film surface for bothspecimens with or without thermal treatment after forming a film. As aresult, the alloy thin film without thermal treatment is separated fromthe glass substrate. On the other hand, as shown in FIG. 29, whenthermally treated for over 20 minutes in temperatures of 200° C. orabove, or over 10 minutes in temperatures of 250° C. or above, the alloythin film was adhered to the glass substrate. Similar tape tests havebeen done to pure Cu thin film, however, separation occurred to all heattreatment conditions. Based on this, it became apparent that favorableadhesiveness to a glass substrate was presented by thermally treating ina temperature of 200° C. or above using the Cu—Mn alloy.

FIG. 28 shows a cross-section TEM image after thermally treating theCu—Mn alloy at 250° C. for 10 minutes. At the top of FIG. 28 is theCu—Mn alloy thin film portion and at the bottom is the glass substrate.A reaction layer having an even contrast is observed along an interfaceof both layers. As a result of analysis using an X ray energy dispersivespectrometer (XEDS) attached to TEM, the reaction layer along theinterface turned out to be an oxide mainly composed of Mn. Forming ofthis oxide is the reason for the improvement in adhesiveness of theinterface.

In order to decrease resistivity, it is ideal to add only enough Mn tosufficiently form the interface layer. For example, when thermallytreating 200 nm alloy film at 250° C. for 10 minutes, an interface layerwith 6 nm thickness is formed. An amount of Mn contained in theinterface layer is approximately 50%, which is equivalent to a pure Mnlayer of approximately 3 nm in thickness. Therefore, a Mn concentrationto be added to the alloy is Mn of 3 parts of 200 in volume ratio, thusCu (1-2) atomic % Mn is ideal considering the density of Cu and Mn. Whenthe thickness of the alloy film is 100 nm, twice the Mn concentration isrequired, and when the thickness of alloy film is 300 nm, ⅔ times the Mnconcentration is required.

Also, FIG. 29 shows the result of adhesiveness evaluation by a tape testafter thermally treating Cn—Mn alloy formed in a film on a glasssubstrate at each temperature for a predetermine time. In this figure, Xindicates separation occurred, Δ indicates separation occurred in somecases, ◯ indicates separation did not occur at all. In addition,separation occurred for pure Cu in all conditions. Based on FIG. 29, noseparation occurred for the present invention in a case of 250° C. orabove.

In addition, in a case of an alloy with more than a sufficient amount ofMn is added to form an interface layer, heat treatment should be done ina high purity Ar gas (oxygen concentration of 0.01 ppm or less)atmosphere that contains oxygen as an inevitable impurity. FIG. 30 showsthe resistivity of an alloy thin film on glass when thermally treated at350° C., and the time evolution of Mn-oxide thickness formed on thesurface. As shown in FIG. 30, Mn remaining in the alloy film afterforming an interface layer can be discharged from the alloy film byreacting with oxygen of less than 0.01 ppm contained in pure Ar andforming an oxide on the surface. As shown in FIG. 30, it became apparentthat the resistivity decreases as the Mn oxide layer on the surfacegrows in thickness. Resistivity after 30 minutes of heat treatmentdecreases to a value equivalent to pure Cu thin film. XEDS analysis ofthe Mn concentration indicated no Mn in the alloy film, which revealedthat excess Mn can be discharged from the alloy film completely.

[Manufacturing Process]

Regarding the liquid crystal display device according to the presentinvention, the oxide layer associated with the copper alloy used as awiring and electrode material of a TFT-LCD, and a manufacturing processof the oxide layer are described below.

FIG. 31 shows the fundamentals of a TFT manufacturing process. Thinfilms 51 of metal, semiconductor, and insulator are respectivelydeposited, and they are patterned by photo-etching using mask 52 andresist coating 53. Sputtering is used for the metal film deposition, andCVD (Chemical Vapor Deposition) is used for the semiconductor andinsulator depositions. For etching, either dry or wet etching is used.The wet etching is often used for the metal to form into the wiring.These steps are repeated four to five times to manufacture a TFT.

Among them, FIG. 32 shows a five-mask process that uses five kinds ofphotomasks for exposure. The process sequence comprises the steps of:(1) forming a gate pattern by wet etching using a mask 1; (2)simultaneously processing three layers of SiN/a-Si/n⁺ a-Si by dryetching using a mask 2 to form a pattern; (3) forming a source/drainelectrode pattern by wet etching using a mask 3; (4) fabricating the n⁺a-Si layer into a channel structure by dry etching using the mask 3; (5)patterning the SiN passivation film using a mask 4; and (6) patterningan ITO (Indium Tin Oxide) film, which is a transparent electrode, usinga mask 5. This allows a TFT substrate to be manufactured.

FIG. 33 shows a cross-section of a structure of a TFT manufactured by astandard five-mask process. As illustrated in FIG. 34, a gate terminalpart constituting an external electrode has a stacked structure of ametal thin film and an ITO film. FIG. 35 shows a plan view of eachpixel.

Selecting an additive element in the copper alloy according to thepresent invention such that the element has oxide formation free energywith a negative value larger than those of elements of an oxide layerenables an oxide film layer to be formed through reduction of theabove-described oxide. Besides, in an oxidative atmosphere, the oxidefilm layer can be formed without the reduction of the oxide.

Further, if the Cu alloy applied as a wiring and electrode material inthe TFT-LCD of the present invention is brought into contact with aninsulation film containing oxygen, the additive element in the Cu alloyis diffused to the interface and thereby the additive element isoxidized to form the oxide film layer.

Still further, metal elements in the insulation layer, and Cu and theadditive element in the Cu alloy form oxides respectively, and theseoxides are combined together to form a compound oxide film. For example,if a TFT substrate contains oxide such as SiO₂, and gate wiring insidethe Cu alloy provided on the substrate is thermally treated, theadditive element in the Cu alloy forming the gate wiring is diffused toan interface between the substrate and the gate wiring and reacts withoxygen in the substrate to form into oxide, which forms an oxide filmlayer.

Also, for example, a gate insulation film 37 consisting of SiNO or thelike is provided on a gate electrode 351, and by applying a thermaltreatment in the manufacturing process, an oxide layer expressed by (Cu,Si, additive element)O_(X) is formed at an interface between the gateelectrode 351 and the gate insulation film 37. In this way, the oxidelayer can be provided on a surface of Cu alloy by using the Cu alloy asa wiring and electrode material for a TFT-LCD.

A method for manufacturing a liquid crystal display device according tothe present invention is provided. The manufacturing process of a TFTsubstrate 11 of the TFT-LCD according to the present invention comprisesa step of depositing copper alloy on a substrate by physical evaporationor chemical vapor deposition, which mainly consists of Cu and forms anoxide layer of an additive element to said Cu on the Cu surface or at aninterface with the substrate; and a step of photo-etching the obtainedcopper alloy film to form at least one of each wiring or each electrode.

In this case, the additive element in the above copper alloy ispreferably at least one type of metal selected from the group consistingof Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd. Also in thiscase, a step of forming an oxide layer on a surface of at least one ofthe formed wiring or electrode may be included.

Also, an oxygen concentration in atmosphere gas used in theabove-described oxide layer formation step is preferably an inert gassuch as argon containing oxygen no less than 1 ppm and no more than 100ppm. Alternatively, argon gas containing oxygen as an inevitable puritymay also be used. Further, the oxide layer formation step may be a stepof forming at least one of the wiring or electrode and then heating at150 to 400° C. for 2 minutes to 50 hours to form an oxide layer of theadditive element in the copper alloy on the surface of at least one ofthe wiring or electrode

A thin film of an alloy was deposited on an insulation film SiO₂ usingCu-2 atomic % Mn alloy comprised of Cu with a purity of 99.9999% and Mnwith a purity of 99.98% as a target material, and thermally treated at atemperature not less than 150° C. and not more than 450° C.Subsequently, a depth compositional profile was analyzed from a surfaceof the thin film using Auger electron spectroscopy.

Also, a cross-sectional sample was prepared, and a cross-sectionalphotograph thereof is shown in FIG. 36. Further, structural observationand compositional analysis were carried out using a transmissionelectron microscope and electron energy-loss spectroscopy (EELS). Oneexample of the results is shown in FIG. 37. A stable oxide layer thatcontains Mn as a main element and has a thickness of a few nm to 20-oddnm is formed around an interface between the Cu—Mn alloy and theinsulating substrate and around a surface of the Cu—Mn alloy.

FIG. 38 shows a variation in film thickness of the oxide layer against athermal treatment time period. Table 2 shows a film thickness of theobtained oxide layer against Mn atomic concentration in the Cu—Mn alloy,a thermal treatment time period, and thermal treatment temperature.FIGS. 26 and 27 shows an enlarged view of a compositional distributionof the oxide layer. The distribution in which Mn has a peak around acenter of the oxide film is exhibited. Cu intrudes from the wiring bodyto the oxide layer; however, the Cu intrusion into the insulation filmis prevented.

TABLE 2 Thickness of formed oxide film layer Atomic concentration inThermal treatment tempareture CuMn alloy Thermal treatment (° C.) (at ·%) time (minute) 350° C. 450° C. 10% 20 min 3.2 nm 6.1 nm 20% 30 min —8.2 nm

Requirements for a sputtering target are provided in the case whereCu—Mn is used as the copper alloy in the liquid crystal display deviceof the present invention. In a TFT-LCD of the present invention, apropagation delay in gate wiring is particularly large. In order toreduce the delay, it is preferable to use copper wiring to providewiring having low resistance close to that of pure copper, as describedabove.

FIG. 39 shows a cross-sectional view of gate wring using Cu—Mn. The gatewiring is comprised of a wiring body 171 and an oxide film layer 172.Parameters a, b, h, t₁, and t₂ in FIG. 39 represents sizes of respectiveparts. a and b are a few μm to 10-odd μm, and h is 200 to 500 nm. t₁ andt₂ are 2 to 10 nm. In this case, in order for the wiring body 171 toprovide low resistivity close to that of pure copper, an amount of Mncorresponding to that contained in the oxide film layer 172 formed by athermal treatment is preferably contained in the wiring body 171, CuMn,before the thermal treatment. Accordingly, a content of Mn that is anadditive element contained in the sputtering target is provided.

[Organic EL]

The present invention is not limited to a TFT liquid crystal displaydevice, but applicable to an organic EL display device. One example oforganic EL according to the present invention is illustrated in FIG. 40.It is mainly comprised of a glass substrate 201; an anode (ITO) 202, ahole transport layer (HTL) 203, an emission layer (EML) 204, and anelectron transport layer (ETL) 205, which are sequentially stacked onthe glass substrate 201; and a cathode 206 arranged on the electrontransport layer 205. For the emission layer, an organic matter such as adiamine system is used. The anode 202 and the cathode 206 areelectrically connected to each other with an electrode line through apower supply. Each of the layers has a thickness of, for example,approximately a few tens of nanometers (nm).

The organic EL display device comprises a scanning line 194, a signalline 195, and a power line 196, which intersect with one another in amatrix form on the substrate 181, and a pixel area 198 surrounded by thescanning line 194, the signal line 195, and the power line 196, and asone example, the pixel area 198 has an organic EL element 191, a drivingTFT 192, and a switching TFT 193.

The organic EL comprises the anode, the hole transport layer, theorganic emission layer, the electron transport layer, and the cathode,which are stacked on the glass substrate. One pixel is comprised of aTFT circuit and the organic EL element, and plurality of pixels arrangedin a matrix form, which is a so-called active matrix organic EL displaydevice.

An equivalent circuit of one pixel is shown in FIG. 41. Also, FIG. 42shows a cross-sectional view of the pixel. For example, on a glasssubstrate 181, there are a driving TFT part 182 and an organic ELelement 184, in which electrodes 183 for a TFT, a cathode 185 made ofmetal, and a transparent electrode 186 are present, and in this example,light 187 is emitted toward a lower part of the substrate.

In the active matrix organic EL display device, unevenness of an imagecaused by a propagation delay of a gate voltage pulse generated in anactive matrix liquid crystal display device occurs. To deal with it,copper alloy is used as a wiring material having high conductivity.

The copper alloy of the present invention is useful for a scanning lineand a signal line. In the organic EL display device according to thepresent invention, at least one of the scanning line, the signal line,the power line, or the TFT electrode uses copper as a main component,and consists of copper alloy that forms an oxide layer of an additiveelement to Cu, which covers wiring or the electrode. A cross-section ofthe wiring is a structure such as FIG. 39.

Further, regarding the copper alloy, copper alloy in which an additiveelement is diffused to a surface of the copper alloy to form an oxidefilm layer of the additive element may be used. Still further, theadditive element may be at least one type of metal selected from thegroup consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd.Still further, the additive element is preferably Mn.

Further, the configuration of the external extraction electrode terminalis preferable to be those of FIGS. 10, 11, 12, 13, and 14.

1. A method for manufacturing a liquid crystal display device (LCD), themethod comprises a step of heat-treating a copper alloy formed on asubstrate at temperatures ranging from 150° C. to 450° C., wherein: anadditional element of the copper alloy reacts with a silicon oxide fromthe substrate forming an oxide, which covers an outer portion of aninterconnection including copper, and the oxide comprises copper (Cu)and silicon (Si).
 2. The method as recited in claim 1, wherein thecopper alloy is transformed into the interconnection including copperafter the heat-treating step.
 3. The method as recited in claim 1,wherein the oxide has a thickness of 1 to 30 nm.
 4. The method asrecited in claim 1, wherein the additional element of the copper alloyis Manganese (Mn).
 5. The method as recited in claim 4, wherein anadditive amount of the manganese is ranging from 0.1 to 25 atom %. 6.The method as recited in claim 1, wherein the heat-treating step isapplied for a time period ranging from 2 minutes to 5 hours.
 7. Themethod as recited in claim 1, wherein the oxide further comprisesmanganese (Mn).
 8. A method for manufacturing a liquid crystal displaydevice (LCD), the method comprises a step of heat-treating a copperalloy formed on a substrate at temperatures ranging from 150° C. to 450°C., wherein: an additional element of the copper alloy reacts with asilicon oxide from the substrate forming an oxide, which covers an outerportion of an interconnection including copper, and a compositionformula of the oxide is Cu_(x)Mn_(y)Si_(z)O (0<X<Y, 0<Z<Y).
 9. Themethod as recited in claim 8, wherein the copper alloy is transformedinto the interconnection including copper after the heat-treating step.10. The method as recited in claim 8, wherein the oxide has a thicknessof 1 to 30 nm.
 11. The method as recited in claim 8, wherein theadditional element of the copper alloy is manganese (Mn).
 12. The methodas recited in claim 11, wherein an additive amount of the manganese isranging from 0.1 to 25 atom %.
 13. The method as recited in claim 8,wherein the heat-treating step is applied for a time period ranging from2 minutes to 5 hours.